Worldwide halloysite deposits, production and market developments

• Autores: Ian Wilson
• Localización: Industrial Minerals, ISSN 0019-8544, Nº. 569, 2015 (Ejemplar dedicado a: Febrero)
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • Halloysite occurs in a number of different colours, as shown in Figure 2. White halloysite is very pure and often hard and porcellaneous. The light brownish halloysite contains goethite, while the red halloysite contains hematite and the black and white halloysite contains blackish manganese.

    The larger deposits are stratiform between a limestone basement and the overlying volcanics. The volcanics are altered by hydrothermal activity with the formation of the halloysite, probably caused by precipitation directly from aluminium- and silica-rich acidic fluids. Pyritisation on the contacts to the halloysite bodies, recrystallisation of the limestones and dissemination of the manganese material at the contact with the limestones are part of the processes that give rise to the halloysite. Alunite, gibbsie and illite are accessory minerals associated with the halloysite.

    Very little is wasted as all the iron-stained halloysite is sold for ceramics. The whiter halloysite is sold in lumps for use in porcelain. The lump halloysite is generally hard with whitish and some with bluish colours. Grade A material has 94-99%, 0.10 % Fe[subscript]2 O[subscript]3 content and content with a loss on ignition % (LOI) of 15-16%. Mineralogically, the material is around 99% halloysite with 1% quartz.